Average ratio of measured flux (numerator) and model predicted flux (denominator) as a function of frequency for all five planets and all Planck-HFI frequencies. For Mars, the predicted thermodynamic temperature has been scaled by ζ_P = 0.982. The thin solid line is the estimated flux density, combining data from all planet observations, while the larger coloured region indicates the combined systematic and statistical uncertainties. Dashed horizontal lines represent the absolute 5% model error envelopes. We note that relative model errors between different frequencies are expected to be less than 5%.